When there are a plurality of elevator cars servicing a facility, the individual elevator cars are assigned or dispatched to respond to a hail call on the basis of a combination of factors. Such factors can include the current direction of travel of each car, the proximity of each car to the origination of the hail call, the weight capacity available of each car, the comparative availability of other cars, as well as other factors. Typically, however, the most widely used factor is the weight of the current load in the elevator car. This information is frequently used to estimate the number of passengers on the elevator car.
Conventional dispatching systems are designed to minimize the mount of waiting time a user experiences between the time the user calls for the elevator car and the arrival thereof. Typically, such systems primarily rely on the weight of the load in the elevator car and, in some instances, the weight distribution within the car. However, in many instances, for example, in businesses, health care facilities, loading areas and freight areas, a user can frequently be frustrated when an elevator car arrives with equipment, a patient, or the like, therein and there is little or inadequate space within the elevator car for oncoming passengers, or other equipment, waiting to enter the elevator car. This condition can result from the inability of current elevator control and dispatching systems to distinguish the actual cross-sectional area occupied by objects and people in an elevator car based upon the weight or weight distribution thereof. One reason for this is that quite frequently the equipment being transported, such as, for example in the case of a health care facility, might be an empty gurney, can be so deceptively light that an elevator car carrying such equipment may appear to have an appropriate remaining weight capacity that the car will be assigned to respond to a hail call when, in fact, because of the cross-sectional area occupied by the gurney, there is little or no room remaining in the elevator car to comfortably receive passengers or equipment.
One known approach to addressing the control of elevators is the system described in U.S. Pat. No. 3,967,702 that teaches a system for monitoring the number of passengers in an elevator car. In that particular system, the number of passengers waiting for an elevator car at each stop having a registered hall call is determined. This information is then used to determine the availability of each elevator car to respond to each particular hall call.
Another system addressing the control and dispatching of an elevator car is taught in U.S. Pat. No. 5,219,042 wherein a plurality of weight sensors are used to determine the number of passengers currently on the elevator car. This system is used to evaluate the overall traffic pattern of the elevators.
In U.S. Pat. No. 5,192,836 a system is taught wherein the space available for passengers is determined based upon the estimated load weight in the elevator car. This system also uses the call condition, i.e., whether of not there is already a hall call for the car from a handicapped person, to determine whether or not a particular car can be dispatched to respond to that call.
A system for detecting the load distribution within an elevator car is taught in U.S. Pat. No. 4,951,786 issued to Haraguchi on Aug. 28, 1990 and assigned to the assignee hereon. Therein, a matrix of weight sensors is disposed in the floor of the elevator car whereby it can be determined if a particular load is a person or a piece of equipment. This information is then used to regulate the response of the car to hall calls.
However, none of these systems provides a full solution to the difficulty faced by passengers confronted with various pieces of equipment when attempting to utilize an elevator. Consequently, it is highly desirable to provide a system and method for determining the availability of an elevator car to respond to hall calls that includes a means for determining the available cross-sectional area of an elevator car which information can then be used as a factor in dispatching an elevator car to respond to a hall call.